DC electrical conductivity retention and acetone/acetaldehyde sensing on polythiophene/molybdenum disulphide composites

In this study, polythiophene (PTh) and a series of polythiophene/molybdenum disulphide (PTh/MoS2) composites were prepared by in-situ chemical oxidative polymerization method using anhydrous ferric chloride (FeCl3) as an oxidant and chloroform (CHCl3) as a solvent. The successful formation of PTh and PTh/MoS2 composites were confirmed by various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance electron microscopy (TEM). DC electrical conductivity and acetone/acetaldehyde sensing studies were carried out by a four-in-line probe device. PTh/MoS2 composites exhibited significantly improved DC electrical conductivity and acetone/acetaldehyde sensing properties as compared to PTh. The electrical properties were investigated in terms of initial conductivity (i.e. conductivity at room temperature) as well as retention of conductivity, i.e. stability under isothermal and cyclic ageing conditions. The maximum initial conductivity, along with the highest conductivity retention, was observed for PTh/MoS2-2 (PTh/MoS2 composite comprising 10% MoS2 with respect to the weight of thiophene monomer). The initial DC electrical conductivity of PTh, PTh/MoS2-1, PTh/MoS2-2 and PTh/MoS2-3 was found to be 5.72 × 10−5 Scm−1, 4.03 × 10−4 Scm−1, 1.09 × 10−3 Scm−1 and 8.96 × 10−4 Scm−1, respectively. The sensing performance at room temperature has been studied in terms of % sensing response, response/recovery time. All the PTh/MoS2 composites based sensors performed much better than PTh. The % sensing response of PTh, PTh/MoS2-1, PTh/MoS2-2 and PTh/MoS2-3 based pellet-shaped sensors towards acetone/acetaldehyde were affirmed as 30.6/22.9, 69.9/47.3, 93.7/70.3, 78.1/65.1, respectively. The purposed sensing mechanism involved the adsorption of acetone/acetaldehyde vapours on the surface of the sensors where electronic interaction between lone pair of electrons on oxygen atoms of the carbonyl group and charge carriers of PTh was responsible for the change in conductivity.

Electrode Fabrication, Material Characterization and Capacitance Measurement Studies of Polyacrylonitrile/Polypyrrole(PAN/PPY) Composite

For the fabrication of the electrode, the Polyvinyl alcohol/polyaniline composite was prepared by the sol-gel method. The electrical conductivity of the composite was determined on compressed pellets by using a 4-in-line-probe dc electrical conductivity-measuring instrument. The electrical conductivity measurement studies revealed that the composite possessed the electrical conductivity in the range of 10-4 to 10-2 S cm-1, i.e., in the semiconductor region and followed the Arrhenius equation. The thermal stability of the composite material (HCl treated) in terms of dc electrical conductivity retention was studied under isothermal conditions (at 50, 70, 90, 110, 130, and 150 °C) at 15 min intervals. The stability of the material (HCl treated) in terms of electrical conductivity retention was also monitored for five cycles at increasing temperatures with 1 h intervals. The composite material was found thermally and environmentally stable in terms of dc electrical conductivity retention.

High Performance n-Type Ag2Se Film on Nylon Membrane for Flexible Thermoelectric Power Generator

Researches on flexible thermoelectric (TE) materials usually focus on conducting polymers (CPs) and CP-based composites; however, it is a great challenge to obtain high TE properties comparable to inorganic counterparts. Here, we report an n-type Ag2Se film on flexible nylon membrane with an ultrahigh power factor ~987.4 ± 104.1 μWm−1K−2 at 300 K and an excellent flexibility (93% of the original electrical conductivity retention after 1000 bending cycles around a 8-mm diameter rod). The flexibility is attributed to a synergetic effect of the nylon membrane and the Ag2Se film intertwined with numerous high-aspect-ratio Ag2Se grains. A TE prototype composed of 4-leg of the hybrid film generates a voltage and a maximum power of 19 mV and 460 nW, respectively, at a temperature difference of 30 K. This work opens opportunities of searching for high performance TE film for flexible TE devices.